In this project, we aim to develop a mass spectrometry (MS) method which has the capability of determining carbon-carbon double bond (C=C) locations in lipids and apply it to qualitative and quantitative lipidomic analysis. This project builds upon an innovation of coupling a photochemical reaction, the Patern-Bchi (PB) reaction, with electrospray ionization and tandem mass spectrometry (ESI-MS/MS). Through collision-induced dissociation (CID), the PB products of lipids fragment at the original C=C positions, allowing both C=C location determination and lipid quantitation for mixtures of lipid C=C position isomers. In this R01 project, research activities are proposed to develop and validate a fully integrated PB-MS/MS approach, with the following aims: (1) development and optimization of reaction and ionization conditions for on-line coupling of Patern-Bchi (PB) reaction with ESI-MS/MS, (2) development of MS/MS methods for structural determination and quantitation of unsaturated lipids of different classes, and (3) implementation and validation of PB-MS/MS method for lipidomic analysis. The Xia research group at Purdue University has the expertise in the development of analytical methods, MS instrumentation, and data analysis tools. The expected outcome from the project is to provide a robust and widely applicable MS platform with C=C specificity for lipidomics. A set of new knowledge will be generated for unsaturated lipids endogenous in rats/mice tissue samples including their C=C position information and composition of C=C position isomers. This new lipid analysis capabilities can potentially advance research in many fields in biological sciences, including but not limited to lipid molecular biology, functional lipidomics, metabolomics, and biomarker discovery.